1. Technical Field
The disclosure relates in general to an apparatus for signal analysis, and more particularly to an apparatus for frequency division and filtering.
2. Description of the Related Art
In the field of signal processing, wavelet transform is widely applied in processing and filtering of signal noise. However, the wavelet transform is applicable to linear and stable signals based on Fourier transform theory. In terms of non-linear and unstable signals, the Fourier transform can only obtain an average distribution of signal energy, but not the information varying with time.
The empirical mode decomposition of Hilbert-Huang transform (HHT) can analyze the tendency of an unstable and non-linear signal varying with time and concretely decompose it into a number of intrinsic mode functions within different frequency ranges. The empirical mode decomposition can also be used to perform filtering processing. For example, electrocardiogram is easily interfered by a lot of noise in the measuring process to influence its judgment, which leads to difficulty of characteristic extraction. Through HHT, noise of the electrocardiogram can be filtered according to different intrinsic mode functions. Besides, the empirical mode decomposition can also be used to analyze unstable and non-linear signals in different fields.
The present HTT or empirical mode decomposition mainly executes relevant algorithm programs by software in a general computer system to verify the input signals after signal processing. However, the conventional software operation is limited in performance and calculation time. Therefore, the technique of HTT or empirical mode decomposition still needs to be improved to increase performance and reduce calculation time so as to meet the requirement of timely processing.